Increasingly it is recognized that cushioning and standard medial support structures, the two historic linchpins of comfort and athletic footwear design, can interfere with natural biomechanics and muscle function such that they may compromise both performance and long-term musculoskeletal health. Typical cushioning mechanisms to absorb shock at initial contact adversely alter proprioceptive input required for appropriate muscle tuning throughout the body, compromising bone health and predisposing to musculoskeletal injury. Moreover, cushioning materials or mechanisms designed to reduce shock at initial contact may actually increase certain knee and hip joint torques or forces which have been linked to the development of knee and hip osteoarthritis.
Although many shoe designs with arch support or medial post support or mechanisms can support the medial side of the foot, including the natural arch of the foot, they affect only the anatomy of the foot and can adversely increase pressure through the medial part of the foot thus also increasing certain torques and forces, in particular knee varus torque, which has been directly linked to the predisposition to knee osteoarthritis. Arch support structures or mechanisms also restrict the natural, yet sophisticated, action of the foot, thereby inhibiting the body's natural, intrinsic mechanism to absorb forces throughout the body. Additionally, standard medial support mechanisms (as well as standard cushioning or shock absorbing mechanisms) that increase coronal or frontal plane joint torques simultaneously reduce efficiency by necessitating increased muscle energy to counterbalance those increased torques.